The present invention relates to an optically-readable value card for use in vending systems for goods or services, and also to a system including such a card.
There are many consumer goods and services which are conveniently purchased directly by the consumer using coins or special tokens. Examples of such services are telephone calls, subway or bus fares, locker rentals, and in some countries, the gas utility. Examples of goods are vending machine articles, such as newspapers, food products and the like. However, the ordinary token-operated or coin-operated systems suffer from several disadvantages. Thus, the labor and infra-structure required for collecting, counting and recycling tokens or coins is disproportionately expensive in many cases to the actual costs of the services or goods. Also, since the tokens or coins have economic value, collection boxes are subject to vandalism and theft. Because of these disadvantages, customer operated vending systems have not been expanded to allow convenient theft-free self-service at gasoline stations and other large scale consumer-oriented products.
Electronically coded value cards have been proposed to avoid the above-mentioned shortcomings of coins and tokens. Two techniques using electronic codes have been suggested. One technique relies on magnetic-tape encoding, but magnetic codes have been proven to be easily forged by methods available even in hobbyist electronic workshops. The other technique relies on expendable read-only memories (ROM) solid-state codes, but ROM memories are too expensive for low-cost services in many cases. Moreover, the state of use of such a value card is not immediately visible to the user.
Another known form of value card includes heat-sensitive optically-readable elements each representing a unit of value for the respective goods or services being vended. The optically-readable element is usually in the form of a thermographic material which is heated to effect the cancellation of the element after the respective item has been vended. Examples of this type of value card are illustrated in U.S. Pat. Nos. 3,873,813; 4,103,150 and 4,143,810.